The present invention relates to a disposable carton for food products or the like and more particularly to a carton formed from lid and tray members which includes an automatic and positive locking means when the carton is closed.
The manufacture of disposable food cartons particularly for the fast food industry involves highly developed technology and competition. Such cartons must be designed for maximum economy and utility with emphasis on ease of handling, filling and closing, product identification, storage of unused cartons and integrity after being filled. When such cartons are used for packaging hot foods, special considerations must be incorporated into the carton design to vent the interior of the carton while still maintaining the packaged products hot. Moreover, since such cartons are used primarily in the fast food industry where speed in handling and packaging is required, there has existed for some time a clear need to provide such a carton with an effective automatic lock.
Various types of foam cartons have been designed and developed for packaging and serving hot foods. Examples of such cartons are shown in the following U.S. Pat. Nos. 3,767,110; 3,968,921; 3,977,595; and 4,383,638. Many of the cartons disclosed in these patents include locking means for the bottom and top members. However, none of the locking means are automatic since they require separate mechanical action or manipulation to insure a positive locking action. Moreover, such cartons are inferior to paperboard cartons in many ways including the inability to print sharp graphics on the outer surfaces thereof and their inherent disposability problems. Accordingly, paperboard cartons are preferred for many applications because of their versatility and economy. In this regard, U.S. Pat. Nos. 4,090,453 and 4,232,816 illustrate examples of paperboard cartons for use in the food industry. However, in each of the patented designs, the locking means for the cartons are not automatic but require a separate manual action for securing the tray and lid components together.
Meanwhile, it is also known from the more general prior art involving the manufacture and design of containers, that effective positive locking means have been used for closures in the past. Examples of such closures are shown in prior U.S. Pat. Nos. 2,190,433; 2,675,160; 3,037,684; and 3,064,877. In each of these patents, effective and positive locking means are disclosed for various containers intended for various uses. However, in each example, the closures cannot be automatically engaged, but require a separate mechanical action to align the locking elements together, or, one or more of the locking elements must be bent from its normal position before it can be utilized. Thus, even though a clear need has existed in the fast food industry for a carton with an effective, positive, automatic locking means upon closure, it has not been obvious to any of the proir workers in the field to design such a package.